This invention relates to compositions for removing coatings from surfaces.
Compositions for removing paints, varnishes, and other coatings have been available for many years. Most of these compositions fall within two general classes. The first type attacks the coating by the chemical action of the ingredients thereof, which generally comprise alkalis or acids. This type of paint remover comprises alkali and acid compositions, such as those described in U.S. Pat. Nos. 3,681,250, 3,615,825 and 3,972,839. There These alkali or acid compositions require considerable after treatment to insure complete removal of the alkali or acid, and have been found to discolor wood. The second type depends upon the solvent power of the constituents of the composition to dissolve or at least soften the coatings. In the second type, it is customary to use aromatic hydrocarbons, lower aliphatic esters, ketones, alcohols, chlorinated solvents, or similar organic solvents. However, the vapor pressure of such liquids is high, with the result that it difficult to keep the paint or lacquer surface wet with the liquid solvent. It has been proposed to overcome this difficulty by adding paraffin wax to such liquid organic solvents to reduce their evaporation rate and thus prolong their contact with the coating to be removed, so that the coating may be sufficiently softened to allow it to be scraped off easily. However, the paraffin wax must be removed in a subsequent step. Although these solvents have received wide usage and have been found to have acceptable stripping qualities, their use is being questioned on the grounds of the health and safety hazards they present to the environment and to the users thereof. U.S. Pat. No. 4,120,810discloses the use of N-methyl 2-pyrrolidone and a mixture of aromatic hydrocarbons having more than six carbon atoms as a paint stripper effective on a wide range of surfaces and capable of penetrating more layers of paint per application primarily because of its slow evaporation rate. This material suffers from the high cost of raw materials and the suspected toxic effects of the aromatic materials used.
U.S. Pat. No. 4,508,634 discloses a composition for removing paint, grease, dirt, and other foreign materials from the skin. The composition comprises propylene carbonate, water, at least one organic cosolvent, at least one thickening agent, at least one neutralizing agent, and at least one surfactant. Although this composition is effective, it has a shelf life that does not generally exceed six months. This limited shelf life is due to the presence of propylene carbonate.
This invention provides an aqueous-based, low-toxicity, non-flammable, thixotropic composition for rendering coatings removable from surfaces.
The composition is an emulsion consisting essentially of (1) at least one dibasic esters, preferably selected from the group consisting of dibasic esters of adipic, glutaric, and succinic acids, (2) water, and (3) at least one thickening agent selected from the group consisting of water soluble and water swellable thickening agents, and mixtures thereof. The amount of dibasic ester or esters in the composition must be sufficient to effectively remove coatings from surface. The amount of thickening agent or agents in the composition must be sufficient to allow the dibasic ester component and water to form a stable emulsion. The composition contains sufficient water to cause the mixture to wet out and adhere to vertical surfaces for a sufficiently long period to insure that the dibasic ester will have sufficient duration of contact with the coating or finish to allow removal of same. The emulsion must contain at least 55% by weight water, preferably at least 60% by weight water, and more preferably at least 70% by weight water.
The composition is effective on a wide range of coatings and surfaces. The composition is useful for rendering organic polymeric coatings and finishes such as paints, varnishes, lacquers, shellacs, gums, natural and synthetic resins removable from such surfaces as wood, metal, and plastic. The composition has also been found to be effective for removing paints, inks, grease, and the like from skin. An important feature of the composition is that it provides excellent results without the need of evaporation retardants or film-forming compounds. Thus, there is no need to include in the formulation such evaporation retardants, as paraffin wax or the like, which have the disadvantage that they need to be removed in subsequent steps. Another feature of the composition is that it has a shelf life in excess of one year.